If the Ooyala HTML5 player is contained on a page embedded in an iframe, it's possible that the full screen button will not work. To get it working again, the iframe containing the webpage will need some additional attributes, such as webkitallowfullscreen, mozallowfullscreen, and allowfullscreen.
For example: <iframe id="my_iframe" name="my_iframe" src="/example/page.html" webkitallowfullscreen="" mozallowfullscreen="" allowfullscreen=""></iframe>
Note that the iframe embed for the Ooyala player includes these attributes by default, so there is no need to add the attributes to the player iframe. However, any iframes containing the player iframe will need to have the attributes added as specified above.